The Minimum Total Mass of MACHOs and Halo Models of the Galaxy

If the density distribution \rho (r) of MACHOs is spherically symmetric with respect to the Galactic center, it is shown that the minimal total mass M_{min}^{{ MACHO}} of the MACHOs is 1.7\times 10^{10}\sol \tau_{-6.7}^{{ LMC}} where \tau_{-6.7}^{{ LMC}} is the optical depth (\tau^{{ LMC}}) toward the Large Magellanic Cloud (LMC) in the unit of 2\times 10^{-7}. If \rho (r) is a decreasing function of r, it is proved that M_{min}^{{ MACHO}} is 5.6\times 10^{10}\sol \tau_{-6.7}^{{ LMC}}. Several spherical and axially symmetric halo models of the Galaxy with a few free parameters are also considered. It is found that M_{min}^{{ MACHO}} ranges from 5.6\times 10^{10}\sol \tau_{-6.7}^{{ LMC}} to \sim 3 \times 10^{11}\sol \tau_{-6.7}^{{ LMC}}. For general case, the minimal column density \Sigma_{min}^{{ MACHO}} of MACHOs is obtained as \Sigma_{min}^{{ MACHO}} =25 \sol { pc}^{-2}\tau_{-6.7}^{{ LMC}}. If the clump of MACHOs exist only halfway between LMC and the sun, M_{min}^{{ MACHO}} is 1.5\times 10^9\sol. This shows that the total mass of MACHOs is smaller than 5 \times 10^{10}\sol , i.e. \sim 10\% of the mass of the halo inside LMC, either if the density distribution of MACHOs is unusual or \tau^{{ LMC}}\ll 2\times 10^{-7}.Comment: 5 pages, 5 Encapsulated PostScript figures, Latex, Accepted for publication in Apj. Letter

The JPL telerobot operator control station. Part 1: Hardware

The Operator Control Station of the Jet Propulsion Laboratory (JPL)/NASA Telerobot Demonstrator System provides the man-machine interface between the operator and the system. It provides all the hardware and software for accepting human input for the direct and indirect (supervised) manipulation of the robot arms and tools for task execution. Hardware and software are also provided for the display and feedback of information and control data for the operator's consumption and interaction with the task being executed. The hardware design, system architecture, and its integration and interface with the rest of the Telerobot Demonstrator System are discussed

Outcomes after decompressive craniectomy for severe traumatic brain injury in children

Journal ArticleObject. Severe traumatic brain injury (TBI) is often accompanied by early death due to transtentorial herniation. Decompressive craniectomy, performed alone or in conjunction with evacuation of the mass lesion, can reduce the incidence of raised intracranial pressure (ICP). In this paper the authors evaluate mortality and morbidity and long-term outcomes in children who underwent decompressive craniectomy for severe TBI at a single institution. Methods. Children with severe TBI who underwent decompressive craniectomy at the Primary Children's Medical Center between 1996 and 2005 were identified retrospectively. Descriptive statistics were used to report postoperative mortality and morbidity rates. Long-term recovery in patients who survived was reported using the King's Outcome Scale for Closed Head Injury (KOSCHI). Fifty-one children with a mean follow-up period of 18.6 months were identified. Nonaccidental trauma accounted for 23.5% of cases. The mean preoperative Glasgow Coma Scale (GCS) score was 4.6. Six patients underwent decompressive craniectomy for elevated ICP only; all other patients underwent decompressive craniectomy in conjunction with removal of the mass lesion. The mean postoperative GCS score was 9.7, and 69.4% of patients had normal ICP levels immediately after surgery. Sixteen children (31.4%) died, including five of six children who underwent decompressive craniectomy for raised ICP alone. Among surviving patients, 2.9% required a tracheostomy, 11.4% required a gastrostomy, 40% experienced posttraumatic shunt-dependent hydrocephalus, and 20% suffered posttraumatic epilepsy requiring antiepileptic agents. The mean KOSCHI score at the last follow-up examination was 4.5 and the mean time to cranioplasty was 2.3 months. Conclusions. Posttraumatic hydrocephalus and epilepsy were common complications encountered by children with severe TBI who underwent decompressive craniectomy. In patients who underwent decompressive surgery for raised ICP only, the mortality rate was exceedingly high

Predicting slitlike ventricles in children on the basis of baseline characteristics at the time of shunt insertion

Journal ArticleObject. Slit ventricle syndrome (SVS) is a delayed complication of shunt insertion and occurs only in children with slitlike ventricles after shunt placement. Although SVS appears to be related to early shunt placement, its predisposing factors are largely unknown. Methods. Baseline data in 737 children who had received shunts were obtained from the databases of two previous clinical trials. Ventricular size before shunt placement and at the last routine follow up was measured using the frontooccipital horn ratio (FOHR). Ventricles with an FOHR less than or equal to 0.2 at follow up were classified as slitlike ventricles. A univariate analysis was performed on data obtained in children with more than 1 year of clinical and radiographic follow up to identify risk factors for developing slitlike ventricles. These results were entered into a multivariate analysis to identify independent predictors of slitlike ventricles. Two hundred forty-four children had more than 1 year of clinical and radiographic follow-up data. The 23 patients (9.4%) who developed slitlike ventricles had shunts inserted at a younger age (42 compared with 134 days, p = 0.09) and were more likely to have developed hydrocephalus secondary to infection (37.5%), head injury (25.0%), or aqueductal stenosis (22.2%). Slitlike ventricles were seen in 10.8% of patients with differential-pressure valves, 10.5% of patients with Delta valves, and 3.6% of patients with Orbis-Sigma valves (p = 0.007). Regression analysis supported the role of the valve type in developing slitlike ventricles. Conclusions. Age at shunt insertion and valve type appear to be the modifiable risk factors for developing slitlike ventricles. If the authors of subsequent studies can further validate these conclusions, slow-draining valves and delayed shunt insertion might be used to decrease the incidence of slitlike ventricles and SVS

Efficient parallel mining of association rules on shared-memory multiple-processor machine

In this paper we consider the problem of parallel mining of association rules on a shared-memory multiprocessor system. Two efficient algorithms PSM and HSM have been proposed. PSM adopted two powerful candidate set pruning techniques distributed pruning and global pruning to reduce the size of candidates. HSM further utilized an I/O reduction strategy to enhance its performance. We have implemented PSM and HSM on a SGI Power Challenge parallel machine. The performance studies show that PSM and HSM out perform CD-SM, which is a shared-memory parallel version of the popular Apriori algorithm.published_or_final_versio

Strain and field modulation in bilayer graphene band structure

Using an external electric field, one can modulate the bandgap of Bernal stacked bilayer graphene by breaking A-~B symmetry. We analyze strain effects on the bilayer graphene using the extended Huckel theory and find that reduced interlayer distance results in higher bandgap modulation, as expected. Furthermore, above about 2.5 angstrom interlayer distance, the bandgap is direct, follows a convex relation to electric field and saturates to a value determined by the interlayer distance. However, below about 2.5 angstrom, the bandgap is indirect, the trend becomes concave and a threshold electric field is observed, which also depends on the stacking distance.Comment: 3 pages, 5 figures - v1 and v2 are the same, uploaded twice - v3, some typos fixed and a reference adde

High-Resolution Scanning Electron Microscopy of Rat Incisor Ameloblasts

The internal three-dimensional organization of secretory and maturation stage ameloblasts was examined using field emission scanning electron microscopy. Particular attention was given to the structure of the Golgi apparatus, the distribution of smooth membrane tubulo-vesicular elements and their relationship with endosomal/lysosomal components. Rat incisors were fixed by intracardiac perfusion with glutaraldehyde, decalcified and divided into segments. The tissues were cryoprotected with glycerol and freeze-fractured. They were then macerated in osmium, and after conductive staining with osmium/tannic acid, the samples were critical-point dried and sputtered with gold. High-resolution scanning electron microscopy showed that ameloblasts contain a well-developed Golgi apparatus, even in the maturation stage where cells are generally believed not to be actively involved in protein secretion. Smooth tubulo-vesicular structures formed a complex network which extended throughout the cell. In secretory stage ameloblasts, this network reached into Tomes\u27 process and consisted of small and large tubules, and distended portions. The smaller tubules radiated from a central core of organelles towards the plasma membrane. Numerous lysosomal/endosomal elements were observed in the Golgi region, and in some cases smooth tubular portions were seen at the surface of multivesicular bodies. These data show that high-resolution scanning electron microscopy can be applied to correlate three-dimensional structural detail with the secretory and resorptive functions of ameloblasts

The influence of inhaled multi-walled carbon nanotubes on the autonomic nervous system

Background: Heart rate and cardiovascular function are regulated by the autonomic nervous system. Heart rate variability (HRV) as a marker reflects the activity of autonomic nervous system. The prognostic significance of HRV in cardiovascular disease has been reported in clinical and epidemiological studies. The present study focused on the influence of inhaled multi-walled carbon nanotubes (MWCNTs) on autonomic nervous system by HRV analysis. Methods: Male Sprague–Dawley rats were pre-implanted with a telemetry device and kept in the individual cages for recovery. At week four after device implantation, rats were exposed to MWCNTs for 5 h at a concentration of 5 mg/m3 . The real-time EKGs were recorded by a telemetry system at pre-exposure, during exposure, 1 day and 7 days post-exposure. HRV was measured by root mean square of successive differences (RMSSD); the standard deviation of inter-beat (RR) interval (SDNN); the percentage of successive RR interval differences greater than 5 ms (pNN5) and 10 ms (pNN10); low frequency (LF) and high frequency (HF). Results: Exposure to MWCNTs increased the percentage of differences between adjacent R-R intervals over 10 ms (pNN10) (p \u3c 0.01), RMSSD (p \u3c 0.01), LF (p \u3c 0.05) and HF (p \u3c 0.01). Conclusions: Inhalation of MWCNTs significantly alters the balance between sympathetic and parasympathetic nervous system. Whether such transient alterations in autonomic nervous performance would alter cardiovascular function and raise the risk of cardiovascular events in people with pre-existing cardiovascular conditions warrants further study